Vaccine-Preventable Disease and the Underutilization of Immunizations in Complex Humanitarian Emergencies

Abstract

Background. Complex humanitarian emergencies (CHE) affect 40 to 60 million people annually. Despite efforts to provide medical and public health services to those affected by CHE, significant morbidity and mortality persist. We argue that vaccination is an essential tool for preventing mortality in CHE that is currently underutilized and poorly standardized. Only measles vaccine is distributed universally in humanitarian crises. All others are considered for use via a decision-making tool created by the Strategic Advisory Group of Experts on Immunization at the WHO, which uses geographic factors, disaster types, and host factors to select appropriate vaccines in emergencies. We hypothesize that the current tool incorrectly assumes variability in vaccine-preventable disease (VPD) across environments experiencing crises. We review the available literature on disease epidemiology in CHE across the globe and discuss implications for vaccine choice and distribution. Methods. We undertook a review of original research and reviews, using MEDLINE, PubMed, SCOPUS, and the databases of the WHO, CDC, UNHCR, UNICEF, and SPHERE. Keywords and focused MeSH terms included: refugee, displaced person, population displacement, disaster, disaster planning, relief work, communicable disease, vaccination and specific diseases and vaccines. All abstracts were assessed for relevance; those deemed topical were reviewed in more detail. Results. Over 200 papers were reviewed and 97 included in the final analysis. Throughout the literature, independent of geography, time, and crisis-type, the two most common causes of death in humanitarian emergencies are acute respiratory illness and diarrheal disease. Within these, the majority of disease is caused by three pathogens: Streptococcus pneumoniae, Rotavirus, and Haemophilus influenzae type-b. Conclusion. A limited number of VPD contribute disproportionately to morbidity and mortality in CHE. The literature suggests that Streptococcus pneumoniae, Rotavirus, and Haemophilus influenzae type-b are essential targets for vaccination programs in emergencies. These three vaccines should be considered for universal use in CHE. Strategies such as reduced dosing schedules and expanded age range of vaccine administration should be investigated to overcome the barriers to distribution.